There are various devices known for positioning or controlling the movement of a cursor on a computer display screen. The most common in use is the conventional "mouse" device, which takes the form of a hand-sized housing which is moved over a flat desktop. Motion over the desktop is sensed by means of a mechanically rotating ball or optically reflective sensor, and digital data are generated which translate into corresponding motion of the cursor on the display screen. Other cursor positioning devices include the graphics input tablet which consists of a flat sensor pad and a hand-held pointing stylus which translates the analog motion of the pointing stylus into digitized data which is used to control the location of the cursor on the display screen. Still other cursor movement devices rely on focused light sources, held by the user or fixed on the user's person, as on a pilot's helmet. Sensors mounted around a display screen track the movement of the light beam and translate this movement into a corresponding movement of the cursor on the display screen.
Devices such as those discussed above are basically effective, although they suffer from certain disadvantages. Most cursor positioning and controlling devices have the disadvantage of requiring a fixed, generally level surface upon which to operate, or must operate in conjuction with a stationary sensor of some type; that is, motion is sensed with respect to a fixed medium and positional data signals are generated and presented to a computer for translation into a corresponding cursor movement. The need for a fixed surface or stationary sensor constrains how the user may interact with the display device. The user must normally sit close to the display screen and be provided with ample level desk space for placement of the graphics tablet or movement of the "mouse." In the case of the stationary sensor, the user must confine movement to keep the light beam within range of the sensor array.
The present invention overcomes the disadvantages of the prior art devices, such as the requirement for a flat desktop or confined movement of a user.